Luminal and basolateral endothelin inhibit chloride reabsorption in the mouse thick ascending limb via a Ca(2+)-independent pathway.
1. The recent localization of endothelin synthesis and receptors in the thick ascending limb (TAL) prompted us to investigate a possible autocrine and/or paracrine effect of this agent. The net chloride flux (JCl) has been determined in isolated cortical and medullary TALs by the in vitro microperfusion technique. 2. In both segments, endothelin 1 (ET-1) at 10(-8) M in the bath significantly decreased JCl, an effect which was partially reversible and observed at concentrations equal to or greater than 10(-13) M. 3. This JCl inhibition (by 33.9 +/- 3.2%) was blocked by BQ788 and was also observed with sarafotoxin 6C and ET-3, indicating that endothelin receptor B (ETB) are present in TAL. 4. ET-1 did not affect cAMP content under basal or hormone-stimulated conditions. The presence of a prostaglandin synthesis inhibitor also did not prevent the ET-1 action on JCl. 5. The ET-1-induced inhibition of JCl was prevented by protein kinase C inhibitors (staurosporine or GF 109203) and was reproduced by diacylglycerol analogues (OAG and DiC8). However, ET-1 failed to increase intracellular Ca2+ concentration. 6. Addition of ET-1 or ET-3 to the apical surface induced a decrease of JCl throgh ETB receptors, an effect which was not additive with that induced by basolateral ET-1, and was not concomitant with an increase in intracellular Ca2+ concentration. 7. It is concluded that the basolateral and luminal inhibitions of JCl by ET-1 in TAL, through ETB receptors, is mediated by a protein kinase C activation which is independent of intracellular Ca2+ increase.
de Jesus Ferreira
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MC
URA CNRS 1859, Département de Biologie Cellulaire et Moléculaire, Gif sur Yvette, France.
Bailly
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C
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism*; D000242:Cyclic AMP / Q000502:physiology; D019332:Endothelin-1 / Q000494:pharmacology / Q000502:physiology*; D004789:Enzyme Activation; D066298:In Vitro Techniques; D008138:Loop of Henle / Q000378:metabolism*; D008297:Male; D051379:Mice; D009434:Neural Pathways / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
D002712:Chlorides; D019332:Endothelin-1; D000242:Cyclic AMP; D011494:Protein Kinases; D002118:Calcium